To investigate the soil behaviors in a direct current field on both spatial and temporal scales, a 1: 5 scale model test was conducted in laboratory to simulate the two-dimensional (2D) electro-osmotic consolidation o...To investigate the soil behaviors in a direct current field on both spatial and temporal scales, a 1: 5 scale model test was conducted in laboratory to simulate the two-dimensional (2D) electro-osmotic consolidation of soft clay foundation. Volume of drainage, intensity, voltage, water content and pH value of water collected in the cathodes were monitored. The pH values of soil and the mass of anodes were measured before and after the test. The test results indicate that the unsaturated state, resultant from fissures induced by the differences in water contents, is favorable to dynamic compaction of soil during electro-osmotic drainage. The results also demonstrate that water content, degree of saturation and electric potential distributions can be used to deduce the electro-osmotic drainage process. Water content of soil decreases first near electrodes, while keeps nearly constant in the center of the model. The area with constant water content is larger than half of the sample surface. Moving anodes towards cathodes by about one third of the electrode spacing is effective to improve the treatment effect after electro-osmosis stops due to the large resistance. Moreover, it is observed that during electro-osmosis, the corrosion rate of anodes becomes smaller, while the variation in pH values of soil near anodes becomes larger.展开更多
Dispersion in time-oscillatory electro-osmotic flows in a slit micro-channel under the effect of kinetic sorptive exchange at walls is theoretically investigated using the homogenization method. The two walls of the c...Dispersion in time-oscillatory electro-osmotic flows in a slit micro-channel under the effect of kinetic sorptive exchange at walls is theoretically investigated using the homogenization method. The two walls of the channel are considered to be made up of different materials, and therefore have different zeta potentials and sorption coefficients. A general expression for the Taylor dispersion coefficient under different zeta potentials as well as various sorption conditions at the walls is derived analytically. The dispersion coefficient is found to be dependent on the oscillation frequency, the Debye parameter, the species partition coefficient, the reaction kinetics and the ratio of the wall potentials. The results demonstrate that the presence of wall sorption tends to enhance the dispersion when the oscillation frequency is low, but the effect is negligible in high-frequency oscillatory flows. Moreover, it is found that the dispersion coefficient could be significantly changed by adjusting the relative wall potentials for low-frequency flows.展开更多
In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering（MPEOD） process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electr...In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering（MPEOD） process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electrical compression（MMPC–DG–MC–EC） stages was established to study the distribution and migration of water, extracellular polymeric substances（EPS）, and other organic matter in the activated sludge（AS） matrix at each stage.Results showed that the MPEOD process could attain 53.52% water content（WC） in dewatered AS with bound water（BW） and free water（FW） reduction rates of 82.97% and 99.67%,respectively. The coagulation and time-delayed magnetic field effects of magnetic microparticles（MMPs） along the MMPC–DG–MC stages initiated the transformation of partial BW to FW in AS. EC had a coupling driving effect of electro-osmosis and pressure on BW, and the changes in pH and temperature at EC stage induced the aggregation of AS flocs and the release of partial BW. Additionally, MMPs dosing further improved the dewatering performance of AS by acting as skeleton builders to provide water passages. Meanwhile, MMPs could disintegrate sludge cells and EPS fractions, thereby reducing tryptophan-like protein and byproduct-like material concentrations in LB-EPS as well as protein/polysaccharide ratio in AS matrix, which could improve AS filterability. At EC stage, the former four Ex/Em regions of fluorescence regional integration analysis for EPS were obviously reduced, especially the protein-like substances in LB-and TB-EPS, which contributed to improvement of AS dewaterability.展开更多
In this paper, we investigate the implications of electro-osmosis on electrohydrodynamic transport of a non-Newtonian fluid on a hydrophobic micro-channel by developing a suitable analytical method. Velocity-slip and ...In this paper, we investigate the implications of electro-osmosis on electrohydrodynamic transport of a non-Newtonian fluid on a hydrophobic micro-channel by developing a suitable analytical method. Velocity-slip and temperature-jump conditions are paid due attention. An attempt has been made to examine the effects of rheological and electro-osmotic parameters on the kinematics of the fluid. The nonlinear Poisson-Boltzmann equation governing the formation of the electrical double layer and the body force that is generated by the applied potential are accounted for in the study. Perturbation solutions are presented. In order to exhibit the applicability of the analysis, the problem of electro-osmotic flow and heat transfer of blood in an arteriole has been taken up as an illustrative example of a real-life problem. An intensive quantitative study has been made through numerical computation of the physical variables involved in the analysis, which are of special interest in the study. The computational results are presented graphically. The study reveals that the temperature of blood can be controlled by increasing/decreasing the Joule heating parameter.展开更多
利用电渗透技术,采用自制装置对市政污水厂的脱水污泥进行深度脱水,研究了机械压力、初始含水率、电压梯度和污泥厚度等对污泥脱水的影响,在此基础上利用响应曲面法,以污泥含水率降低率为响应指标,根据BoxBenhnken中心组合实验设计,对...利用电渗透技术,采用自制装置对市政污水厂的脱水污泥进行深度脱水,研究了机械压力、初始含水率、电压梯度和污泥厚度等对污泥脱水的影响,在此基础上利用响应曲面法,以污泥含水率降低率为响应指标,根据BoxBenhnken中心组合实验设计,对污泥电渗透脱水工艺参数进行了优化。结果表明,电渗透技术可以改善污泥的脱水性能,当机械压力为18.83 k Pa,污泥厚度为1.13 cm,电压梯度为60 V/cm,初始含水率为87.45%时,污泥含水率可降至49.14%。展开更多
基金Supported by the National Natural Science Foundation of China (50879076)
文摘To investigate the soil behaviors in a direct current field on both spatial and temporal scales, a 1: 5 scale model test was conducted in laboratory to simulate the two-dimensional (2D) electro-osmotic consolidation of soft clay foundation. Volume of drainage, intensity, voltage, water content and pH value of water collected in the cathodes were monitored. The pH values of soil and the mass of anodes were measured before and after the test. The test results indicate that the unsaturated state, resultant from fissures induced by the differences in water contents, is favorable to dynamic compaction of soil during electro-osmotic drainage. The results also demonstrate that water content, degree of saturation and electric potential distributions can be used to deduce the electro-osmotic drainage process. Water content of soil decreases first near electrodes, while keeps nearly constant in the center of the model. The area with constant water content is larger than half of the sample surface. Moving anodes towards cathodes by about one third of the electrode spacing is effective to improve the treatment effect after electro-osmosis stops due to the large resistance. Moreover, it is observed that during electro-osmosis, the corrosion rate of anodes becomes smaller, while the variation in pH values of soil near anodes becomes larger.
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region,China(Grant No.HKU 715510E)
文摘Dispersion in time-oscillatory electro-osmotic flows in a slit micro-channel under the effect of kinetic sorptive exchange at walls is theoretically investigated using the homogenization method. The two walls of the channel are considered to be made up of different materials, and therefore have different zeta potentials and sorption coefficients. A general expression for the Taylor dispersion coefficient under different zeta potentials as well as various sorption conditions at the walls is derived analytically. The dispersion coefficient is found to be dependent on the oscillation frequency, the Debye parameter, the species partition coefficient, the reaction kinetics and the ratio of the wall potentials. The results demonstrate that the presence of wall sorption tends to enhance the dispersion when the oscillation frequency is low, but the effect is negligible in high-frequency oscillatory flows. Moreover, it is found that the dispersion coefficient could be significantly changed by adjusting the relative wall potentials for low-frequency flows.
基金supported by the National Natural Science Foundation of China(Nos.51478041,51678053)Major Projects on Control and Rectification of Water Body Pollution(Nos.2012ZX07105-002-03,2013ZX07202-010)
文摘In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering（MPEOD） process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electrical compression（MMPC–DG–MC–EC） stages was established to study the distribution and migration of water, extracellular polymeric substances（EPS）, and other organic matter in the activated sludge（AS） matrix at each stage.Results showed that the MPEOD process could attain 53.52% water content（WC） in dewatered AS with bound water（BW） and free water（FW） reduction rates of 82.97% and 99.67%,respectively. The coagulation and time-delayed magnetic field effects of magnetic microparticles（MMPs） along the MMPC–DG–MC stages initiated the transformation of partial BW to FW in AS. EC had a coupling driving effect of electro-osmosis and pressure on BW, and the changes in pH and temperature at EC stage induced the aggregation of AS flocs and the release of partial BW. Additionally, MMPs dosing further improved the dewatering performance of AS by acting as skeleton builders to provide water passages. Meanwhile, MMPs could disintegrate sludge cells and EPS fractions, thereby reducing tryptophan-like protein and byproduct-like material concentrations in LB-EPS as well as protein/polysaccharide ratio in AS matrix, which could improve AS filterability. At EC stage, the former four Ex/Em regions of fluorescence regional integration analysis for EPS were obviously reduced, especially the protein-like substances in LB-and TB-EPS, which contributed to improvement of AS dewaterability.
基金Science and Engineering Research Board, Department of Science and Technology, Government of India, New Delhi for the financial support of this investigation through (Grant No. SB/S4/MS: 864/14)
文摘In this paper, we investigate the implications of electro-osmosis on electrohydrodynamic transport of a non-Newtonian fluid on a hydrophobic micro-channel by developing a suitable analytical method. Velocity-slip and temperature-jump conditions are paid due attention. An attempt has been made to examine the effects of rheological and electro-osmotic parameters on the kinematics of the fluid. The nonlinear Poisson-Boltzmann equation governing the formation of the electrical double layer and the body force that is generated by the applied potential are accounted for in the study. Perturbation solutions are presented. In order to exhibit the applicability of the analysis, the problem of electro-osmotic flow and heat transfer of blood in an arteriole has been taken up as an illustrative example of a real-life problem. An intensive quantitative study has been made through numerical computation of the physical variables involved in the analysis, which are of special interest in the study. The computational results are presented graphically. The study reveals that the temperature of blood can be controlled by increasing/decreasing the Joule heating parameter.
文摘利用电渗透技术,采用自制装置对市政污水厂的脱水污泥进行深度脱水,研究了机械压力、初始含水率、电压梯度和污泥厚度等对污泥脱水的影响,在此基础上利用响应曲面法,以污泥含水率降低率为响应指标,根据BoxBenhnken中心组合实验设计,对污泥电渗透脱水工艺参数进行了优化。结果表明,电渗透技术可以改善污泥的脱水性能,当机械压力为18.83 k Pa,污泥厚度为1.13 cm,电压梯度为60 V/cm,初始含水率为87.45%时,污泥含水率可降至49.14%。
